The digital representation of content is known. Content includes, but is not limited to, music, video, program code, text and graphical documents, images, interactive presentations, etc. The content is generally encoded in accordance with a pre-set standard to create encoded content, such as a file or streaming media. Each standard generally specifies a protocol for encoding content such that it may be stored or transmitted, and a protocol for decoding content that has been encoded to reconstruct the content for playback. These standards are known as document types, and may involve protocols called codecs. The encoded content can be stored on digital media such as a hard disk drive, a floppy disk, an optical media disk, flash memory, volatile memory or, alternatively, can be transmitted via a communications network. As both storage and network bandwidth have associated costs, such codecs are generally designed to compress the digital representation of the content while maintaining a desired level of quality. For music, a number of codecs exist, including MP3, AAC and WAV. Similarly, for still images, the codecs include, but are not limited to, JPEG, GIF, PNG and TIFF. A number of codecs exist for video, including MPEG-2, MPEG4, AVI and WMV. Similarly, other encoding schemes for other types of computer-readable content exist, such as plain text, document files (e.g., Microsoft Word and Excel documents), program files (e.g., executables and dynamic link libraries) and interactive media (e.g., Microsoft PowerPoint and Macromedia Shockwave files).
A feature of encoded content is that there are currently few limitations on the ability to reproduce any number of identical copies of the encoded content and distribute it freely without identifying the source of the copies. This ability to make unlicensed copies of encoded content is an artifact of how computers operate. The replication of encoded content is also an artifact of how the majority of communications networks are designed, in that they reproduce data transmitted across them, regardless of the type of data.
In many circumstances, it is desired by the owners of encoded content to limit its unauthorized access, copying and dissemination. There are, however, no widely-implemented mechanisms in current communications protocols or hardware that control the authorized use of the data being processed. That is, computers that use communications protocols to connect to networks, such as the Internet, and that exchange encoded content, do not have sufficient logical controls automatically to determine the proprietorship, source or rights associated with the encoded content that is being processed, hence the complete inability to govern its distribution.
In order to control the distribution and use of such encoded content, some content proprietors have implemented digital rights management systems. Such systems store encoded content in an encrypted digital format that corresponds to an encryption key, and rely on a non-standard application to decrypt the encoded content at the time of presentation or playback. These systems, however, require the use of specialized players and/or content viewers, hereinafter referred to as “decoders”, that are capable of decrypting the encoded content, thereby limiting the selection of decoders available to end-users and/or causing compatibility issues. For example, music content licensed to a person by a proprietor employing a particular digital rights management scheme may only be accessible via a particular decoder application on a particular operating system, and may not be decodable via a traditional hardware appliance, such as a compact disk player.
Further, as the encoded content in such digital rights management systems includes the totality of the data representing the content, successful cryptanalytic attacks can ultimately permit access to the entire content.
There are a number of other schemes for restricting access to content which require specialized devices such as a non-standard decoders or physical hardware. Still others employ traditional cryptography and are therefore vulnerable to the same class of cryptanalytic attacks against their restriction mechanisms because the attacker has the entirety of the encoded content. In these cases, only the computational problem of generating the correct decryption key needs to be solved in order to unrestrict the entirety of the content, which can then be copied in a repudiable manner.
Current systems for distributing authorized encoded content may include license identifiers only as a non-essential part or extension of the functional part of the data structure of an encoding scheme, like a credit at the end of a film, or a notice in the headers of a file. As the content itself is not affected, however, the content can be separated reasonably easily from the marked encoded content.
File-sharing services, such as Internet-based Kazaa and Limewire, are under pressure from content proprietors to distinguish between encoded content which may be shared freely from that for which the proprietors' permission is required. Without the ability to preclude the unauthorized distribution of encoded content, such services risk liability.
Since existing popular codecs for encoded content do not have standardized features to identify the terms of authorized use and/or the individual licensed to use the encoded content, there is no consistent or automatic way for file-sharing services to assess whether or not the sharing of encoded content via their networks is unauthorized.
Ultimately, in these cases, since the end-user possesses the entirety of the content, the content can potentially be decrypted and copied or distributed in their entirety in a repudiable manner.